Building out a ported enclosure for a Dayton Audio RSS390 HO subwoofer, tuned to 23Hz. Materials will be a combination of luan / baltic birch for the bent laminations, MDF & baltic birch for the flat surfaces. Tentatively planning to finish the 4 verticals in Tolex "leather", with the top / bottom finished in lacquered zebrawood veneer.

So, without further ado...all the images! Also, critique's and suggestions / guidance welcome.

The plans, first just raw dimension, the second showing bracing placement:

cab and port are a *little* on the small side, but if space is limited, it should work fine.

winisd overestimates tuning frequency by a smidge, so it'll probably come in around 21-22 which is fine.

eq requires more power, so all other things equal, 3db requires 2x power at that point.

room gain will also increase the very low end unless you have a giant room, so get it in place before worrying about how much eq will be needed.

what amp are you planning to pair with this one?

Yeah, size is an issue for this sub and where it's gonna be located. I could go an inch or two more on the depth, but the height and width of the cab is pretty much fixed. On the room gain, when I ran the ARC on the Anthem, it listed the room gain at 4.85dB, but didn't list a particular frequency. Not sure if that's the same as the gain you're referring to. I have a UMIK and MiniDSP on order, so once I get the sub built and in place, I'll get to learn REW.

The plan is to power this one with a bridged XLS1002. I've also been toying with the idea of just going for an XLS2502, and running it stereo to both subs at 4ohm. I already have one sub, a sealed Ultimax 15 in a 3.4 ft^3 cabinet running off a bridged XLS1002. Adding a second 1002 would be cheaper than switching both to a 2502. But I have options.

If there were tweaks you'd make to the design, as far as cab size / port size, I'm definitely open to suggestions. I do want to keep the curved sides...those are based on an 8ft diameter circle, with a segment at 23º. Playing around in WinISD, I was trying to keep a close eye on port velocity and excursion, but I admit, I don't know how closely those graphs translate to real-world use.

depending on the nature of the driver and design, the model can translate pretty well.

with height and width dimensions limited and rounded sides as a design feature, I'm not sure you can do much better than you have.

go for it!

I'm not exactly sure how your room gain is being calculated, but if it is around 4-5db at 20hz, this is very roughly speaking how that might look.

also, a good starting point for eq is to put on a 2nd order butterworth on or a hair below the tuning frequency, then use a parametric eq q=2.0, gain=2.5dB, with the same frequency to bring output back up, but not require any additional excursion (well, it requires a hair more) or power (than before the eq).

also, a good starting point for eq is to put on a 2nd order butterworth on or a hair below the tuning frequency, then use a parametric eq q=2.0, gain=2.5dB, with the same frequency to bring output back up, but not require any additional excursion (well, it requires a hair more) or power (than before the eq).

First, with this box / port / eq configuration, am I in danger of either bottoming out or over-extending this sub given the intent to drive it with a bridged XLS1002? It claims 1100watts @ 4ohms bridged. Realistically speaking, I rarely (and I do mean rarely) watch movies above the -20 setting on the Anthem MRX-720. Most of the time, we watch between -35 and -25 depending on the baseline volume gain of the content provided. That given, there are still those occasions where movies really boost that LFE channel requiring excursion & power, so I want to be sure I don't blow this thing up during the first movie.

Second, I had planned on adding some internal damping using some pyramid or egg-crate style acoustic panels. How will this affect the internal volume (if at all), and how do I dampen the port? Do I run some denim or closed-cell foam half way up the port or do I not even bother? Since I can build the port somewhat independent of the enclosure, I plan on sanding, sealing, and lacquering the port interior walls to minimize surface resistance. The internal end will be rounded over and the external end will be flared.

@LTD02
Second, I had planned on adding some internal damping using some pyramid or egg-crate style acoustic panels. How will this affect the internal volume (if at all), and how do I dampen the port? Do I run some denim or closed-cell foam half way up the port or do I not even bother?

+1 on this. I have some old Auralex crates that I need to use up. I don't know if it would cover every wall corner. I'm in a similar scenario where my space is really limited so every inch (literally) counts.

...
First, with this box / port / eq configuration, am I in danger of either bottoming out or over-extending this sub given the intent to drive it with a bridged XLS1002? It claims 1100watts @ 4ohms bridged. Realistically speaking, I rarely (and I do mean rarely) watch movies above the -20 setting on the Anthem MRX-720. Most of the time, we watch between -35 and -25 depending on the baseline volume gain of the content provided. That given, there are still those occasions where movies really boost that LFE channel requiring excursion & power, so I want to be sure I don't blow this thing up during the first movie.

spec sheet shows about 1100 watts bridged output from that amp. that takes the driver to about 15mm excursion, which should be just fine. xmax in the spec is overhang on that driver, not useful excursion limit, and the damage point is well out beyond even that. in your enclosure that should be fine.

Quote:

Originally Posted by protectedvoid

Second, I had planned on adding some internal damping using some pyramid or egg-crate style acoustic panels. How will this affect the internal volume (if at all), and how do I dampen the port? Do I run some denim or closed-cell foam half way up the port or do I not even bother? Since I can build the port somewhat independent of the enclosure, I plan on sanding, sealing, and lacquering the port interior walls to minimize surface resistance. The internal end will be rounded over and the external end will be flared.

if you do include it, try to stay away from the port. there are some instances where damping the port may be beneficial, but that would come at the expense of reduced low end output.

Quote:

Originally Posted by tjcinnamon

+1 on this. I have some old Auralex crates that I need to use up. I don't know if it would cover every wall corner. I'm in a similar scenario where my space is really limited so every inch (literally) counts.

if running a sealed stuffing may give a tiny increase in efficiency on the very, very low end. see same link above.

where some sort of stuffing has its advantages are in mains as well as in very large enclosures where internal standing waves may interfere with the response.

if running a sealed stuffing may give a tiny increase in efficiency on the very, very low end. see same link above.

where some sort of stuffing has its advantages are in mains as well as in very large enclosures where internal standing waves may interfere with the response.

I should add the caveat that my build is a 40Hz to 160Hz ported MBM .

From the article: If you are looking for the utmost in uncolored and well-damped sound or if you intend to use the system extra high in frequency up into the lower midrange, it is recommended.

Would auralex be considered using internal volume? Would the safest option just be the pillow stuffing away from the port? I think some stuffing will help with internal resonances of the higher frequencies but I can't afford any loss in volumetric cuft

spec sheet shows about 1100 watts bridged output from that amp. that takes the driver to about 15mm excursion, which should be just fine. xmax in the spec is overhang on that driver, not useful excursion limit, and the damage point is well out beyond even that. in your enclosure that should be fine.

So, since I don't have a vacuum press or a large steam box, I had to build a clamping jig to assist in creating the bent lamination sides for the enclosure. And since it's a build thread, I'm gonna include how I made the jig.

So, to begin, the curvature of the sides is an arc created by an 8ft diameter circle. So I needed a jig over 4ft long, and configured to have exactly 48" between the centers.

Once that was done, I needed to cobble together a setup that would position my blank appropriately to successfully route the curve.

Curve routed. This will be the template for the top/bottom of the enclosure + a primary component of the clamping jig.

For the clamping jig, I need several of these curves to create a base on which the plywood can be lain. So, rough sized blanks were cut on the table saw, with the majority of the waste removed via jigsaw (the bandsaw is next on the equipment purchase list). Then, my handy template tape, careful alignment, and some time spent on the router table.

Next, I needed a series of clamping cauls, so I planed some 2x2's to give me consistent thickness and flat faces. To avoid moisture imbalance, all sides were planed. I then rounded over the edges and drilled three sets of holes in each caul for threading.

And now, how it all comes together. Tie down straps will be used to apply sufficient clamping force across the arrangement of cauls to ensure a solid, void-free glue bond between each ply.

Next steps are to cut the luan to rough size and glue up the side laminations.

Thanks. I totally lifted the design from a bluetooth speaker I saw on Amazon, so I didn't originate it and can't really take credit for it. But I did have to adapt it to this build. If I had it to do over, I would have added more bracing inside and probably would have gone with 1/2" baltic birch laminated over 3/4" MDF. This cabinet is all MDF.

Thanks. I totally lifted the design from a bluetooth speaker I saw on Amazon, so I didn't originate it and can't really take credit for it. But I did have to adapt it to this build. If I had it to do over, I would have added more bracing inside and probably would have gone with 1/2" baltic birch laminated over 3/4" MDF. This cabinet is all MDF.

So, by more bracing I probably mean more & different. I would have done 4 U braces forming a tic-tac-toe pattern instead of the cross-bracing I used. I get some panel flex on the top panel because, like an idiot, I only have one cross-brace through the center of the top panel.

As for the BB + MDF, this is what I meant:

The left side of that image shows how I pulled this design together. The right side shows how, in hindsight, I should have designed it. Cabinet grade BB, even in 1/2" thickness, is very ridged with 7 plies of equal thickness. So, leaving 1/8" of the BB after routing the design still leaves me ~2ply of ridged material with a full glue-bond to the substrate. That same 1/8" in MDF would be ****...which is why I ended up just making all the individual polygons for the design out of 1/2" MDF and gluing them to the substrate. The problem with the approach I took is that those polys are not "connected" to each other, so the center top panel has a loud resonance at ~125Hz. The room correction on my Anthem receiver crossed the subs over at 110Hz, so there are certain times during movies/music where that resonance is audible. Crossing the subs over at 90Hz eliminates that resonance, but that also means I had to manually tweak the ARC settings.

@Shreds
-- So, after doing some pricing, it's actually cheaper for me to buy rough-cut zebrawood and mill it myself and make the finished top / bottom out of solid zebrawood instead of veneer. Go figure.

Are you sourcing it locally? Is that because you'd have to buy a sheet of it vs. small strips of the rough-cut or something like that? Hopefully they aren't banging ya on the head too bad for the price. Either way solid gives more bragging rights anyway.

So, by more bracing I probably mean more & different. I would have done 4 U braces forming a tic-tac-toe pattern instead of the cross-bracing I used. I get some panel flex on the top panel because, like an idiot, I only have one cross-brace through the center of the top panel.

The left side of that image shows how I pulled this design together. The right side shows how, in hindsight, I should have designed it. Cabinet grade BB, even in 1/2" thickness, is very ridged with 7 plies of equal thickness. So, leaving 1/8" of the BB after routing the design still leaves me ~2ply of ridged material with a full glue-bond to the substrate. That same 1/8" in MDF would be ****...which is why I ended up just making all the individual polygons for the design out of 1/2" MDF and gluing them to the substrate. The problem with the approach I took is that those polys are not "connected" to each other, so the center top panel has a loud resonance at ~125Hz. The room correction on my Anthem receiver crossed the subs over at 110Hz, so there are certain times during movies/music where that resonance is audible. Crossing the subs over at 90Hz eliminates that resonance, but that also means I had to manually tweak the ARC settings.

[/QUOTE]

I'm not seeing where the 1/2" MDF was affixed to the 3/4" in your design specs. Was that for the baffle?

Did you use polyfill or something like that to dampen the resonance? LTD02 recently posted an article from data-bass about the effects of poly-fill or other dampening materials in sealed, ported, and horn designs. One of the conclusions as that it helped reduce resonances at mid to higher bass frequencies.

I'm not seeing where the 1/2" MDF was affixed to the 3/4" in your design specs. Was that for the baffle?

So, this sub is my existing UM15-22. I probably muddied the waters here a bit, but someone asked what the clamping cauls were resting on, hence the photos of the black cube. The design specs at the top are for the second sub I'm building, which is for the Dayton 390HO sub in a ported cab, which is the build this thread is dedicated to.

Quote:

Originally Posted by tjcinnamon

Wow! So that much bracing wasn't enough. You used glue and screws correct

Yes. Titebond 2, clamping force, plus screws for extra support. The sidewalls don't seem to have an issue and the double-baffle definitely doesn't. It's just the top of the box that has a problem (where bracing is concerned).

Quote:

Originally Posted by tjcinnamon

Did you use polyfill or something like that to dampen the resonance?

Yes, in the cube sub, I used a little over 3lbs of Acousti-Stuff "polyfill", based on the recommendation from one of the techs at PE.

Yes, in the cube sub, I used a little over 3lbs of Acousti-Stuff "polyfill", based on the recommendation from one of the techs at PE.

Ahhh makes sense. The older design. I see why you had the double layer to get those grooves in. I wonder if Green Glue between the 3/4 and 1/2" boards would have helped dampen that resonance.

I making an MBM so I have to be extra careful about resonance. I have some old Auralex but I'm not sure if they desinty would classify as lost cuft or not. How did you determine how much bracing? I like your tic-tac-toe design.

To be honest, I just guessed. The theory (as I understand it) is, the more you subdivide a panel into smaller "squares" that is then cross-braced to at least 2 other surfaces, the more rigid the panel becomes, and therefore less prone to flexing. The "resonance" I'm referring to is likely due to those 1/2" MDF polygons vibrating in response to top panel flex. It could be I didn't get as tight a glue-bond on a few of them where I forgot to nail the centers down with brads.

This is all speculation, of course, because I can't put enough weight on the top during playback to see if that's the case, but it feels like a "thing". I kinda feel like I shouldn't get smacked in the head when resting my ear on the top of the cabinet during bass-intensive tracks if that top panel was properly braced.

That's a sweet design on your um15. The extra work you'll do for the curved cab will be worth it in the end. The veneer is the easiest part

Thanks. As I mentioned earlier, I can't take credit for the design. I just used it to give the big cube a more interesting exterior.

I've always like curved cabinets, and I've got a fair amount of practice at bent lamination (just on smaller projects). The plans don't show it, but I'll be adding top & bottom "vanity" pieces to finish off the design. Those will be slightly proud of the cabinet on all 4 sides. That's what will get veneered. If I want to keep it cheap(er), I could go with some tiger maple veneer. That stuff's not too expensive. The zebrawood veneer is kinda pricey, so I may just go all out with solid zebrawood top/bottoms. Unless I can find someone locally to resaw it for me.

So, not a lot happened this week with kids and work, but I managed to get the clamping jig assembled. I used a shop made story stick to make sure all the holes were evenly and consistently spaced, and another shop made jig to make sure the holes in the bottoms of the curve pieces all lined up consistently and correctly.

Then, I glued and clamped the side panels. They will each be a total of 4 layers thick, but I've only glued the first 3 layers together to form the curve. The forth layer will go on after these have been attached to the top, bottom, and braces, completely covering the attaching screws.

Made some more progress today. I picked up some marine-grade baltic birch today. Luckily I only needed enough for the top / bottom and rear of the sub. After tax, a 2ft x 4ft piece was $35. Anyway, drew out a rough template to gauge placement and minimize waste. I'd already cut the piece for the rear at this point.

Time for the lock miter. Call me a coward, but this is probably one of the only router bit that scares me. This and panel bits. Anyway, double feather boards to help apply pressure at the bit to make sure I get a good profile cut. Because this is a miter cut, I use some template tape and a straight edge to provide a guide for the piece against the fence after the miter has been cut.

After the miters have been cut, I removed the excess ply from the drawn template, then use the curve guides to route those curves.

So, the front and rear panels, which are cut to size already, need to have their long edges cut to match the profile of the curve. So....rather than using the angle gauge, I just used the top panel to set the angle of the blade on the table saw for the front / rear panel edge cuts.

After making sure the miter cuts are good, and that I've successfully matched the curve angle for those front and rear panels, it's time for a quick dry fit test. The left / right sides will be trimmed before final assembly.

And finally, I started the vent.

Tomorrow, I'll route the dados for the vent into the top / rear panels. I'll also route the dados for the braces. And, feet willing, my goal tomorrow is to get all the braces done, test run assembly, trim the side panels to final size and get the front baffle going.